International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 8 - October 2015
Non Linear Analysis of Jacketed Reinforced Concrete Column
Nishad C S#1, Jerry Anto*2
#1
PG Student, #2Assistant Professor
Civil Engineering Department, Ilahia College of Engineering and Technology Mulavoor, Ernakulam, Kerala, India
Abstract - Jacketing of reinforced concrete column is to target
the improvement of local vulnerabilities in columns related to
inadequate strength (compressive & Flexural) or poor
ductility. Theoretical analysis have been carried out in the
present study for different column sections of jacket thickness
of 50 mm and 75mm and 100 mm for jacketed RC columns
subjected to uni-axial compressive loading.
Nonlinear finite element analysis has been carried
out for the jacketed RC columns. In order to find out the
increase in the confined capacity of jacketed columns due to
strengthening with respect to original column, theoretical
analysis has been carried out.
The uni-axial load carrying capacity along both the axes
(major and minor) has been carried out under balanced
section condition. ANSYS is used for the FEA analysis.
Keywords— Jacketed column, Ansysn14.5, Ultimate load
carrying capacity.
I. INTRODUCTION
Concrete is a structural material, used extensively in
the construction of various kinds of buildings. Even though it
is a structural material, it is very difficult to increase its
strength once it sets. Many issues are to be dealt with during
its service condition such as substantial detailing of the steel
reinforcement and deterioration of the concrete under severe
environmental conditions. Problems associated with the
deterioration of concrete are usually due to corrosion of the
reinforcing steel and spalling of the concrete. Thus,
retrofitting measures must be taken to maintain the integrity of
the structure. Traditional repair and rehabilitation methods
include concrete jacketing and steel jacketing. Concrete
jacketing requires intensive preparation of formwork and
increases the weight and size of the strengthened member.
Steel jacketing is a labour-intensive technique that is costly,
heavy, difficult to handle, and prone to corrosion. Therefore,
there is an urgent need to develop a more reliable repair and
rehabilitation system. Understanding the response of the
composite before and after strengthening during loading is
crucial to the development of an overall and efficient and safe
structure. Many methods have been utilized to study the
response of structural components. Experimental based testing
has been widely used as a means to analyse individual
elements and the effects of concrete strength under loading.
While this is a method that produces real life response, it is
extremely time consuming, and the use of materials can be
quite costly. The use of finite element analysis to study these
components has also been used. In recent years, however, the
use of finite element analysis has increased due to progressing
knowledge and capabilities of computer software and
ISSN: 2231-5381
hardware. It has now become the choice method to analyse
concrete structural components. The use of computer software
to model these elements is much faster, and extremely costeffective.to fully understand the capabilities of finite element
computer software, one must look back to experimental data
and simple analysis. Data obtained from a finite element
analysis package is not useful unless the necessary steps are
taken to understand what is happening within the model that is
created using the software. Also, executing the necessary
checks along the way is key to make sure that what is being
output by the computer software is valid.by understanding the
use of finite element packages, more efficient and better
analyses can be made to fully understand the response of
individual structural components and their contribution to a
structure as a whole. This thesis is a study of reinforced
concrete columns with or without concrete jacketing using
finite element analysis to understand the response of
reinforced concrete column under compression loading.
II. SCOPE AND OBJECTIVE
RC Column with and without jacketing is modelled in
Ansys 14.5 for loading in both X and Y direction. Modelled
columns were analysed to find out the ultimate load carrying
capacity of various column with and without jacketing having
varying jacketing thicknesses.
The scope of present work includes the development of a
precise analytical model, to obtain the behaviour of column
under the given load condition and the study on concrete
jacketed and without jacketed specimens give the suitability of
jacketing to be used in strengthening of columns. The concrete
jacketing enhanced the performance of the columns by
postponing the rupture of the concrete and reinforcement,
which means, it increased the column ductility.
III. DESCRIPTION OF GEOMETRICAL AND
MATERIAL PROPERTIES USED
The accuracy of the structural analysis using
numerical methods depends on the representation of the
behaviour of material under different state of stresses and
loading conditions. The details of the properties employed for
finite element modelling are given in table
The grade of the concrete considered is 20N/mm2. Details of
the sections considered and reinforcement provided are given
in the tables below. Stirrup spacing has been calculated as per
IS456-2000.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 8 - October 2015
TABLE 1. GEOMETRICAL AND MATERIAL PROPERTIES
Original column
dimensions (mm)
230x450, 300x300, 300x450
Column height (mm)
3000
Jacket thickness (mm)
50, 75 and 100
IV. MODELLING IN FINITE ELEMENT
The cad modelling of column is carried out using
finite element software i.e, ANSYS 14.5. The type of analysis
carried out in ANSYS is Non-linear static analysis. First we
have to model a concrete control column specimen and with
this we can generate the model of concrete jacketed column.
The size of column used for modelling are
230X450X3000mm, 300X300X3000mm, 300X450X3000mm.
The cross section of reinforcement used are 25mm, 20mm,
16mm and 10mm dia for main steel bar and 8mm dia for
lateral ties. The lateral ties are provided at a spacing of
200mm, 250mm and 300mm.
The 3-D modelling of column is carried out by generating the
volumes in active coordinate system. Figure 5.2 shows the
model of concrete control column specimen.
Original column concrete and Jacketing concrete
Modulus of
Elasticity(N/m2)
Poisson’s ratio
0.2
Longitudinal Reinforcement and Stirrups
Modulus of
Elasticity(N/m2)
Poisson’s ratio
0.3
TABLE 2. DIMENSIONING DETAILS OF ORIGINAL AND
JACKETED COLUMN
Original
column
dimension
(mm)
Jacketed column dimension
Stirrup
spacing
(mm)
For
50mm
jacketing
For
75mm
jacketing
For
100mm
jacketing
230x450
330x550
380x600
430x650
200
300x300
400x400
450x450
500x500
300
300x450
400x550
450x600
500x650
250
Figure 1. Model of original column
A. Element Type
Element
no:
1
TABLE 3. REINFORCEMENT DETAILS OF ORIGINAL AND
JACKETED COLUMN HAVE SAME SPACING FOR ORIGINAL
COLUMN AND JACKETED COLUMN
type
Material used
Element used in
ANSYS
concrete
Solid 65
B. Real constants
The real constants for this model are found out using.
Longitudinal steel provided
Original
column
(mm)
Original
column
50
(mm)
75
(mm)
100
(mm)
Stirrup
spacing
(mm)
230x450
4#20+4#16
10#10
4#20
6#20
200
300x300
4#20+4#16
8#10
4#20
8#16
300
300x450
4#25+4#16
10#10
8#16
6#20
250
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Real Constant Set 1 is used for the Solid65 element. It
requires real constants for rebar assuming a smeared model.
Values can be entered for Material Number, Volume Ratio,
and Orientation Angles.
C. Elemental properties
Material Model Number 1 refers to the Solid65
element. The figure shows the simplified compressive uniaxial
stress strain curve for the concrete and the table gives the
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 8 - October 2015
value of stress and strain input to get the graph after solving
the above equations.
TABLE 5. MATERIAL PROPERTIES FOR STEEL
Steel
Linear Isotropic
Material
No:2
Ex
2.1 e11 N/m2
PRXY
0.3
Bilinear Isotropic
Figure 2. Simplified compressive uniaxial stress- strain curve for concrete
Yield Stress
415 e6 N/m2
Tang Modulus
20 e6 N/m2
TABLE 4. MULTI LINEAR ISOTROPIC PROPERTIES OF
CONCRETE
D. Meshing
Points
Strain
Stress
To obtain good results from the Solid65 element, the
use of a rectangular mesh is recommended. The overall
mesh of the volume is shown in figure.
(N/mm2)
1
0.00036
9.802
2
0.00060
15.396
3
0.00130
27.517
4
0.00190
32.103
5
0.00243
33.096
Implementation of the Willam and Warnke (1974)
material model in ANSYS requires that different constants be
defined. These 9 constants are:
Shear transfer coefficients for an open crack
= 0.2
Shear transfer coefficients for a closed crack
=1
Uniaxial tensile cracking stress
= 3.78N/mm2
Uniaxial crushing stress (positive)
= 40 N/mm2
Biaxial crushing stress (positive)
=0
Ambient hydrostatic stress state
=0
Biaxial crushing stress (positive)
=0
Uniaxial crushing stress (positive)
=0
Stiffness multiplier for cracked tensile condition. = 0
Figure 3. Mesh diagram of the model
E. Loading and Boundary Conditions
The hinged support is provided at the top end of the
column and fixed support is provided at the bottom end of the
column. The force is applied along negative Y-axis and
negative X-axis of the model. The force applied in the model
is obtained from STAAD by modelling a G+3 building in
STAAD Pro software.
V. ANALYSIS OF THE MODEL
The finite element model for this Non-linear analysis is a
simple column under compressive loading. For the purposes
of this model, the Non-linear static analysis is utilized. The
Solution Controls command dictates the use of a linear or nonlinear solution for the finite element model. Here in this thesis
the analysis is carried out for non-linear and small
displacement. The tables 6.1 define the loads provided in the
column.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 8 - October 2015
TABLE 6. LOADS PROVIDED ON COLUMN
FX
FY
(kN)
(kN)
230x450
8.813
1372
300x300
10.607
1395
300x450
12.939
1426
Original column
dimension (mm)
VI. RESULTS AND DISCUSSIONS
Figure 7. Displacement of column 300x450 mm without jacketing
A. Load deflection curves
The deflection obtained for the column with different
column dimensions are illustrated below
Figure 4. Displacement of column 230x450 mm without jacketing
Figure 8. Load deflection curve for column 230x450mm with and
without jacketing
Figure 5. Displacement of column 300x300 mm without jacketing
Figure 9. Load deflection curve for column 300x300mm with and
without jacketing
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 8 - October 2015
REFERENCES
[1] Anushree and Vijay Kumar Y M, “Finite Element Analysis of Jacketed
Reinforced Concrete Column Subjected to Uni-axial Load”, International
Journal of Research in Engineering and Technology, vol.03, 2014
[2] Hajsadeghi M and Alaee F J, “Numerical Analysis of Rectangular
Reinforced Concrete Columns Confined With FRP Jacket Under
Eccentric Loading”, The 5th International Conference on FRP
Composites in Civil Engineering, September 27-29, 2010 Beijing, China.
[3] Charalambidi B G, Rousakis T C and Karabinis A I, “Finite Element
Modeling of Reinforced Concrete Columns Seismically Strengthened
through Partial FRP Jacketing”, Laboratory of Reinforced Concrete,
Figure 10. Load deflection curve for column 300x450mm with and
without jacketing
VII. CONCLUSIONS
The following conclusions were arrived based on the
analytical investigation conducted on column strengthened
using various jacketing thicknesses.
1. Strengthening techniques can be adopted as a feasible
solution for enhancing the compression capacity of concrete
member.
2. Confinement of concrete was achieved by jacketing the
specimen with concrete. The compressive behaviour of the
specimens was enhanced due to the confinement pressure
exerted by the strengthening material.
3. The cracking behaviour of the specimen was enhanced due
to the presence of concrete jacket, the crack initiations were
reduced due its high tensile capacity.
4. The deflection of the column decreases as the cross section
of the column increases.
Department of Civil Engineering, Democritus University of Thrace,
Greece
[4] Jaya K P and Jessy Mathai, “Strengthening of RC column Using GFRP
and CFRP”, Hindustan Institute of Technology and Science, Chennai,
India.
[5] Pezhman Taghia and Suhaimi Abubakar, “Mechanical Behavior of
Confined Reinforced Concrete-CFRP Short Column-Based on Finite
Element Analysis”, World Applied Sciences Journal, 2013.
[6] Alper
Buyukkaragoz,
“Finite
Element
Analysis of
The
Strengthened With Prefabricated Reinforced Concrete Plate” Scientific
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[7] Antonio F. Barbosa and Gabriel O. Riberio. “Analysis of Reinforced
Concrete Structures using ANSYS Nonlinear Concrete Model.”
Computational Mechanics. pp.1-5, 1998.
[8] Saifullah,
M.Nasir-uz-zaman,
S.M.K.Uddin,
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and
M.H.Rashid. “Experiment and Analytical Investigation of Flexural
Behaviour of Reinforced Concrete Beam.” International Journal of
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5. Deflection also got decreased as the thickness of jacketing
increased.
6. The ultimate load carrying capacity also got increased for
jacketed column than column without jacketing.
7. The jacketed concrete is about 25% to 30% stronger than
the column without jacketing.
ACKNOWLEDGEMENT
I wish to thank the Management, Principal, and Head of
Civil Engineering Department of Ilahia College of
engineering and technology, affiliated by Mahatma Gandhi
University for their support. This paper is based on the work
carried out by me (Nishad C S), as part of my PG course,
under the guidance of Mr.Jerry Anto (Assistant Professor,
Ilahia College Of Engineering & Technology Mulavoor)
Ernakulam, Kerala, India).The fruitful interactions held with
Mr. Jerry Anto during my project are duly acknowledged.
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